Simultaneous achievement of high performance and high
reliability in a 38/77GHz InGaAs/AlGaAs PHEMT MMIC
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Citation
Hisaka, Takayuki, et al. "Simultaneous achievement of high
performance and high reliability in a 38/77GHz InGaAs/AlGaAs
PHEMT MMIC." IEICE Electronics Express Vol. 7 (2010) , No. 8
pp.558-562
As Published
http://dx.doi.org/10.1587/elex.7.558
Publisher
Institute of Electronics, Information and Communication
Engineers
Version
Author's final manuscript
Accessed
Wed May 25 21:46:30 EDT 2016
Citable Link
http://hdl.handle.net/1721.1/59830
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Attribution-Noncommercial-Share Alike 3.0 Unported
Detailed Terms
http://creativecommons.org/licenses/by-nc-sa/3.0/
IEICE Electronics Express, Vol.* No.*,*-*
Simultaneous achievement
of high performance and
high reliability in a 38/77GHz
InGaAs/AlGaAs PHEMT
MMIC
Takayuki Hisaka,1a) Hajime Sasaki,1 Takayuki Katoh,1 Ko
Kanaya,1 Naohito Yoshida,1 Anita A. Villanueva, 2 and Jesus A
del Alamo2
1
High Frequency & Optical Device Works, Mitsubishi Electric Corporation,
4-1 Mizuhara, Itami, Hyogo 664-8641, Japan
2
Department of Electrical Engineering and Computer Science, Massachusetts
Institute of Technology,
Room 39-567, Cambridge, MA 02139, USA
a) Hisaka.Takayuki@cw.MitsubishiElectric.co.jp
Abstract: In order to meet the demand for mass production of 77 GHz
automotive radar systems, a low cost and high performance 38/77 GHz
AlGaAs/InGaAs PHEMT MMIC transmit amplifier with a multiplier has
been realized. The chip is packaged in an inexpensive conventional
non-hermetic package. Excellent power performance is demonstrated with a
15 dBm output power and 7 dB maximum conversion gain from 38 to 76.5
GHz. Also, highly reliable RF operation of a bare MMIC chip is obtained
with less than 0.7 dB reduction in output power during 106 hr at Vd=4 V and
Ta=25 ºC in air.
Keywords: PHEMT, reliability, MMIC, humidity, automotive radar
systems, non-hermetic package
Classification: Electron devices
References
[1] S. Sugitani, T. Ishii and M. Tokumitsu, “Three-dimensional interconnect with
excellent moisture resistance for low-cost MMICs,” IEEE Trans. Adv. Packag.,
vol. 26, no. 2, pp.133-140, 2003.
[2] Y. Aihara, T. Kitano, K. Miyawaki, “High gain plastic mold package HEMT,”
Mitsubishi Electric Report, pp.47-50, 2005.
[3] T. Hisaka, H. Sasaki, Y. Nogami, K. Hosogi, N. Yoshida, A. A. Villanueva,
J.A.del Alamo, S. Hasegawa, H. Asahi, “Corrosion-induced degradation of
GaAs PHEMTs under operation in high humidity conditions” Microelectronics
Reliability 49, pp.1515-1519, 2009.
© IEICE 2008
[DOI: **.****/*****************]
Received September **, 2008;
Accepted September **, 2008;
Published in October **, 2008 issue
[4] A. A. Villanueva, J. A. del Alamo, T. Hisaka, T. Ishida, “Drain corrosion in RF
1
IEICE Electronics Express, Vol.* No.*,*-*
power GaAs PHEMTs,” IEDM Tech. Dig., pp.393-396, 2007.
[5] UMS CHU2277 http://www.ums-gaas.com/all-products-selection-guide.php
[6] Y. Kawano, T. Suzuki, M. Sato, T. Hirose, K. Joshin, “A 77GHz Transceiver in
90nm CMOS,” IEEE International Solid-State Circuits Conf. Dig. 18.3, 2009.
1. Introduction
One of the most promising commercial applications for millimeter-wave systems
is automotive radar to provide active safety for driving. Recently, the demand for
low cost AlGaAs/InGaAs pseudomorphic HEMT (PHEMT) MMICs that are
suitable for this application is emerging. In order to reduce the cost of the devices,
there has been wide interest in the last few years in the use of non-hermetic
packages [1]. To survive in non-hermetic packages, GaAs devices must have
resistance to humidity. Thicker passivation films or other polymer coatings on the
devices without hermetic sealing have been widely used to protect the device
surface [2]. These films and coatings degrade the high-frequency characteristics
due to their parasitic capacitance. In order to simultaneously meet the demand for
high performance and low cost, there is a need for a highly reliable high-power
AlGaAs/InGaAs PHEMT technology that withstands high humidity conditions.
We have previously reported a comprehensive study of degradation of
AlGaAs/InGaAs PHEMTs during operation under high humidity conditions [3-4].
We have concluded that PHEMT degradation is caused by an electrochemical
corrosion reaction between the semiconductor and H2O that takes place at the
SiNx/semiconductor interface on the drain side of the device. We also
demonstrated that a special surface treatment to reduce oxygen at the
semiconductor surface can effectively suppress the degradation without any loss of
RF performance [3]. In the present work, we have adopted the surface treatment in
the fabrication of 38/77 GHz MMICs transmit amplifier using AlGaAs/InGaAs
PHEMTs for automotive radar. In this paper, we demonstrate the high reliable and
high performance of 38/77 GHz bare-chip MMICs without a hermetic package.
2. Experimental
Double heterostructure AlGaAs/InGaAs PHEMTs [3] with around 0.2 µm gate
length were fabricated for this study. The gate region was wet-chemically recessed
to a desired drain current and metalized with Ti/Al for the gate electrode. These
devices were passivated with a silicon nitride film by plasma-enhanced chemical
vapor deposition (PECVD). Just prior to the deposition of the passivation film, a
surface treatment that consists of dipping the wafer in a benzenoid-aromatic
-compound-based organic solvent was performed. The treatment effectively
reduces the amount of As-oxide at the semiconductor surface as reported
previously [3].
© IEICE 2008
Fig. 1 shows the chip photograph of a 38/77 GHz transmit amplifier fabricated in
this study. The MMIC consists of a frequency doubler and a 4-stage 77 GHz
[DOI: **.****/*****************]
Received September **, 2008;
Accepted September **, 2008;
Published in October **, 2008 issue
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IEICE Electronics Express, Vol.* No.*,*-*
amplifier. The chip area is 3.17 x 1.17 mm2. The PHEMT MMICs were fabricated
with 3 different processes that are: (a) without the surface treatment (b) with
surface treatment, (c) with polymer coating. The relative permittivity (k) of the
polymer is 2.5. The polymer coating was formed after the SiNx passivation film
deposition [2].
×2
38GHz
77GHz
Fig. 1.
Photograph of a top of view of 38/77 GHz transmit amplifier
with multiplier. The chip area is 3.17 x 1.17 mm2
3. Results and discussions
Fig. 2 shows on-wafer measurement results of the conversion gain (Gc) as a
function of output power (Pout) at fin = 38 GHz and fout = 76.5 GHz of MMICs chips
fabricated with the three different processes. The schematic cross sections of the
three device structures are also shown in Fig.2. Sample (c) with a polymer coating
shows a 3.5 dB decrease in maximum Gc compared with the sample without
surface treatment. This is caused by an increase of the parasitic capacitance. On the
other hand, sample (b) with surface treatment shows almost the same Pout and Gc as
sample (a) without surface treatment. This result shows that the surface treatment
is more effective especially for high frequency devices compared with the widely
used polymer coating. A Pout of 15 dBm and maximum Gc of 7 dB were obtained
for sample (a) with surface treatment. These results show an excellent performance
for 77 GHz automotive applications that is comparable to that of state of the art
devices [5-6].
Surface treatment
8
P in = 12dBm
f = 76.5 GHz
Conversion gain (dB)
7
SiNx
Gate
Source
GaAs
InGaAs
AlGaAs
Drain
H+ Ion
Implantation
(a) without surface　treatment　(conventional)
6
(b) with the new surface
treatment
5
4
SiNx
3
2
1
0
3
5
7
9
11
Output power (dBm)
© IEICE 2008
Polymer coating
13
15
(c) with polymer coating
(without surface treatment)
Fig. 2.
Comparison of on-wafer measured output power (Pout) at Pin =
12 dBm, f = 76.5 GHz of 38/77 GHz transmit amplifier MMIC with 3
different processes: (a) without any surface treatment, (b) with the new
surface treatment, and (c) with polymer coating.
[DOI: **.****/*****************]
Received September **, 2008;
Accepted September **, 2008;
Published in October **, 2008 issue
3
IEICE Electronics Express, Vol.* No.*,*-*
Fig. 3(a) shows the change in Imax (ΔImax) as a function of stress time during DC
bias humidity test (relative humidity (RH) = 85%, ambient temperature (Ta) = 85
ºC, Vds = 4 V, Ids = 1/2 Idss) of bare-chip MMICs.. Imax is the drain current measured
at Vg = +0.6 V and Vds = 1 V. Imax changes less than 5% after 1000 hr. Other DC
characteristics also do not show any significant change.
Fig. 3(b) shows the change in Pout (ΔPout) of bare-chip MMICs during RF life test
(Ta =25 ºC, Vds =4 V, fout =77 GHz, Pin =15 dBm), exposed in air during the test.
The extrapolated ΔPout to 106 hr operation is less than -0.7dB. These results show
that the transmit MMICs with the new surface treatment simultaneously deliver
the required RF performance and a high reliability even when exposed to air. This
is very attractive for low-cost MMICs for automotive applications that do not use
expensive conventional hermetic packages.
Change in I max (%)
20%
T a=85 ºC, RH = 85%,
V d= 4V, I ds=1/2 I dss
10%
0%
-10%
-20%
0
200
400
600
Time (h)
800
1000
(a) Imax change during humidity test
Change in output power (dB)
0
-0.2
0.7dB
-0.4
-0.6
-0.8
-1
-1.2
Ta = 85 ºC, in air
Vd= 4V, Ids = 1/2 Idss
-1.4
-1.6
100
101
102
103
104
105
106
Time (h)
(b) Pout change during RF life test in air
Fig. 3.
Highly reliable results of 38/77 GHz transmit amplifier bare-chip
MMICs with a new surface treatment. (a) Imax change during humidity test. RH
=85%, Ta = 85 ºC Vds = 4 V, Ids=1/2 Idss. (b) Pout change during RF life test in air. Ta =
R.T., Vds = 4 V, fin=38 GHz, fout=77 GHz, Pin =15 dBm.
© IEICE 2008
[DOI: **.****/*****************]
Received September **, 2008;
Accepted September **, 2008;
Published in October **, 2008 issue
4
IEICE Electronics Express, Vol.* No.*,*-*
4. Conclusion
We have developed high performance and highly reliable AlGaAs/InGaAs
PHEMT MMICs for 77 GHz automotive radar systems by means of a new surface
treatment. The 38/77 GHz transmit MMIC achieves an output power of 15 dBm
and a conversion gain of 7 dB at 76.5 GHz. We demonstrate highly reliable RF
operation of a bare chip MMIC exhibiting less than 0.7 dB reduction in output
power during 106 hr at Vds=4 V, Ta=25 ºC in air. We believe that these results are
promising for low cost and high performance 77 GHz AlGaAs/InGaAs PHEMT
MMICs for automotive applications without using conventional hermetic
packages.
Acknowledgments.
The authors wish to thank Dr. T. Sonoda, Y. Nogami, Y. Aihara, A. Hasuike for
helpful discussions. They also wish to thank K. Yuasa, D. Tunami, and M. Totuka
for performing the experiments of the process and for useful discussion. They also
would like to thank Prof. H. Asahi, Assoc. Prof. S. Hasegawa of Osaka University
for valuable discussions.
© IEICE 2008
[DOI: **.****/*****************]
Received September **, 2008;
Accepted September **, 2008;
Published in October **, 2008 issue
5